General Notes. 



imens. The sknll of the type (that of the other specimen is missing) 

 lacks the mandible and the cutiré basal part ol braincase, though the 

 remaining portiorj is in fair condition. It has certain peculiarities not 

 shared by any of the five sknlls of R. nelsoni: the postorbital processes 

 are broader and heavier, the palate is more arched between toothrows, 

 and the dorsal profile of braincase is less bent downward posteriorly. 

 These cranial characters are, however, quite within the range of normal 

 variation in niembers of tlie family. I consequently have n<> hesitation 

 iu regarding the later ñame nelsoni as a synonym of diazi. Mr. E. W. 

 Nelson, who examined the specimens with me, is of the saine opinión.» 



Measurements of the type specimens (those of R. "nelsoni" in paren- 

 thesis): hind foot, 48.6 (53); ear from crown, 38.6 (37); greatest Iength 

 of skull, 60.4 (60.6); zygomatic breadth, 294 (30.4); breadth of brain- 

 case, -2.6 (23.4); postorbital constriction, 10.0 (9.8); interorbital con- 

 striction 9.8(10.0); nasal, 24.4+ (24.8); greatest breadth of both nasals 

 together, 9.8 (10.0); diastema, 16.0 (15.8); Iength of palate (lateral), 

 7. t (7.8); width of palate between anterior premolars, 8.0(7.6); width 

 of palate between posterior niolars, ln.4 (10.6); depth at middle of 

 palate, 13 6 (14.0); maxillary toothrow (alveoli), 11.6 ( 12.0). 



Note. — Four specimens (Nos. 174531—4) collected at Textlananquila 

 mi Mount Iztaccihuatl, above Amec.ameca, and presented to the ü. S. 

 National Museum by Professor Ferrari-Pérez, arrived in Washington 

 after this article was in type. They entirely confirm the identity of 

 Romerolagus diazi and R. " nelsoni". 



—Gerrit S. Miller, Jr. 



* In vie« of Mr. Nelson's personal acquaintance with the región where the two 



i \ pes wer llected I rcquested him to give a brief accountof the geography. This 



he has kindls done as follows : "The total aria occupied l>> Romt rolagus appears to be 

 limited to the middle slopes of the voléanos Popocatepetl and iztaccihuatl. The 

 boundary line between the States of México and Puebla runs along thecrests of these 

 mountaius in a northerly and southerly course, thus placing the western slopes in 

 México and theeastern oues in Puebla. These mountaius are ioiued by a broad ridge 

 about 12,000 feet bigh, ateach end of wbich risethe high peaks. The middle slopes, 

 w here Romt rolayus lives are continuous around both mountains and lie in an área 20 

 miles long, in :i norto and south direction. and ten miles broad, from east towest. 

 Romerolagus lives permanently onlj whereit has the shelter of the coarse saccaton 

 grass and ile- áreas occupied i>.\ this plant aro broken by hot slopes on which it can not 

 maintain itself. These breaks are n<>t wide and can be readily crossed by sroal] 

 uiammals The extremely limited área which Romerolagua occupies.and theabsolute 

 identity of climatic and other physical conditions within it, appear to preclude the 

 possibility oí the existence of more than one local Eorm." 



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